A method of generating a mold and using it for printing a three-dimensional object

ABSTRACT

This invention relates to three-dimensional printing. This invention in particular relates to a method of generating mold and printing a three-dimensional object. The mold thickness is controlled and holes are generated in the mold surface for releasing moisture easily. The mold surface having holes is designed initially digitally and then combined with the three-dimensional model before printing the three-dimensional object. In case the thickness of the mold surface is more then it reduces the overall quality of the three-dimensional object. When the model is enclosed inside the mold, there will be some residue moisture in the model even if the drying apparatus can improve this by drying layer by layer. This affects the final quality of the part. A solution of these problems is provided in the present invention. The thickness of the mold layer is between 0.5 to 1 mm and holes having 0.1 to 0.4 mm diameter. The holes are evenly distributed on the mold. The mold having the holes is prepared from which moisture can easily escape. A method of digitally generated a mold having thin layer and holes is used for fabricating three dimensional objects with high precision and quality.

FIELD OF THE INVENTION

The present invention generally relates to the field of three-dimensional (also “3-D”) printing of objects based on a crafting medium and molding techniques. The invention, particularly relates to a method of generating a mold (“mould”) and printing a three dimensional object. An advantage of the present invention is that it provides a mold of desired skin thickness for containing a crafting medium. The mold thickness is controlled during via the printing process. Furthermore, perforations or holes are generated in the mold surface to facilitate drying and moisture release after printing.

BACKGROUND OF THE INVENTION

Three-dimensional printers are used to build solid models by performing layer by layer printing of building materials. The building material can be of different forms, such as liquids or semi-liquids at the three-dimensional printhead. For example, a solid material can be heated and then extruded from a three-dimensional printer nozzle. The layers of building materials can be solidified on a substrate. Three-dimensional printer systems can use a fused filament fabrication (FFF) process (sometimes called fused deposition modeling (FDM) process) in which a filament is moved by a filament moving mechanism, toward a heated zone. The filament can be melted and extruded on a platform to form a three-dimensional object. The melted filament can have the disadvantage of adhering to the walls of the heated printhead, resulting in deformed printed lines. A commercially available FFF system uses a heated nozzle to extrude a melted material like a plastic wire. The starting material is in the form of a filament which is being supplied from a spool. The filament is introduced into a flow passage of the nozzle and is driven to move like a piston inside this flow passage. The front end, near the nozzle tip, of this piston is heated to become melted. The rear end or solid portion of this piston pushes the melted portion forward to exit through the nozzle tip. The nozzle is translated under the control of a computer system in accordance with previously generated computer-aided design (CAD) data sliced into constituent layers. Further, the additive manufacturing devices and processes are largely used for creating very complex three-dimensional objects and also for creating body part materials. In known physical reconstructing methods, a CAD system either is directly sending signals to the devices or converting it to the any suitable file format. Various additive techniques are used for three-dimensional printing.

The manufacturing of precision components is performed with exceptional control and either post process characterization or in situ characterization or both. For larger or complex structures it is very challenging, or not even possible, to make very large or complex objects with exceptional precision. For achieving high quality and precision, it is important to prepare digitally generated molds, to print the molds having high quality, while also leaving no residue on the surface of the object upon removal of the mold material.

A number of different types of accessories for three-dimensional printing are available in the prior art. For example, the following patents are provided for their supportive teachings and are all incorporated by reference: Prior art document, EP3301597 discloses a method for computationally designing a re-usable flexible mold having a verified cut layout for reproduction of objects having rich surface details or complex shape structures. The re-usable flexible mold is prepared by three-dimensional printing. The mold has a wall thickness between 1 to 5 mm, more preferably between 2 to 3 mm, and further the mold wall also has holes. The reference appears to disclose a liquid casting material but does not appear to disclose the use of a paste or crafting material in conjunction with the mold. Further, the reference does not appear to disclose either the formation of a removable mold or the use of any crafting medium.

Another prior art document, IN201621002997 discloses a device for controlling particle collection in a continuously flowing multi-particle water-based liquid-particle suspension system. The reference appears to discuss the incorporation of holes with a mold and also discloses fabrication of the mold by three-dimensional printing. However, this prior art document does not appear to discuss a layer-by-layer deposition and the use of crafting material.

Yet another prior art document, U.S. Pat. No. 5,121,329 discloses an apparatus for making three-dimensional physical objects of a predetermined shape by sequentially depositing multiple layers of a solidifying material on a base member in a desired pattern. The reference does not appear to disclose the formation of a mold or the use of any crafting medium.

Yet another prior art document, US20160332388 discloses a method of forming transparent three-dimensional objects. The three-dimensional object is printed based on a three-dimensional image file. An image analyzer recognizes a three-dimensional position of the independent structure based on the three-dimensional image file. The three-dimensional position of the independent structure can be expressed as a point at which at least two imaginary lines cross each other. The image analyzer generates a three-dimensional image file for a mold having penetration holes through which imaginary lines pass, and the three-dimensional printer prints the mold. The three-dimensional printer can print a mold having penetration holes through which two imaginary lines pass so as to indicate the position of the independent structure. Next, the independent structure is fixed by inserting supports through the penetration holes of the mold. This reference suggests that the holes in the mold are made in which the support structure material is inserted. Further, this prior art document does not appear to discuss the use of a crafting material paste.

Yet another prior art document, CN106694880A discloses a manufacturing method for a copper alloy special-shaped hole cooling mold. The manufacturing method comprises the following steps: (i) a three-dimensional digital mold of the copper alloy special-shaped hole cooling mold is built, and the three-dimensional digital mold is derived in stereolithography (“STL”) format; (ii) the three-dimensional digital mold from the first step is treated and repaired for meeting the requirement of three-dimensional printing; (iii) the three-dimensional digital mold obtained in the second step is subjected to arrangement angle analysis, grid support addition, process allowance addition, and bottom chamber manufacturing; and (iv) the three-dimensional digital mold treated in the third step is converted into two-dimensional slice information, including error diagnosis and repair, where a machining program file is generated, and the machining program file is imported into the three-dimensional printing equipment. However, the prior art document does not appear to discuss the use of paste crafting materials.

Yet another prior art document, US2016299494 discloses automated structures using modular structures and real time feedback for high precision control. An apparatus includes a rigid frame or girder system, a first computer-controlled motion system associated with the rigid frame or girder system and configured to move in coordinated positions, a second computer controlled motion system associated with a part to be worked on and configured to move in coordinated positions is disclosed. In one of the examples, a mold is printed and polished and measured with defined tolerances and then the object (e.g., a dish) is on the mold and then separated. Separation is challenging given the vast surface area. Inducing small holes throughout the mold that can force air into the dish will allow the dish to be lifted without damage. Small holes are induced throughout the mold however, the purpose of preparing the holes is to remove the dish, and not to facilitate drying of the object or evaporation of solvents.

Yet another prior art document, SE1500245 to Mats Moosberg discusses a three-dimensional imaging process for making objects, preferably metal objects or ceramic objects, on a layer-by-layer basis under the control of a data processing system. The process also includes the use of a filament material (in the form of a solid that melts to a fluid during the printing process) to build the mold and a crafting medium (in the form of paste) for filling the hollow mold cavity. The method for building the three-dimensional model by extruding a crafting medium in parallel with a molding material as described in the prior art document, SE1500245, requires that the crafting medium paste is dried after the creation of the object. The drying process is evacuating all water from the paste and leave a dry “green body”, similar to dried clay. The problem which needs to be addressed here is that the paste needs to be dried evenly to avoid cracks. It is also important that the paste is dried fully in the middle to avoid problems in the next steps. Also, the method for building the 3D model by extruding a crafting medium in parallel with a molding material as described in the prior art document, SE1500245, is difficult to use for some heavy geometries or overhanging geometries.

However, above mentioned references and many other similar references have one or more of the following shortcomings: (a) do not adequately discuss the preparation of a re-usable mold; (b) employ a thick layer of the mold for preparing complex structures whereby the subsequent removal of the mold to provide a high quality surface area is challenging; (c) do not discuss a molding technique; (b) do not discussing the use of a paste form of a building or crafting medium; (d) these prior art three-dimensional printing methods use a powder clay which is mixed with water and printed out on a layer by layer basis using a syringe to obtain ceramic objects; (e) the resulting ceramic objects can have low resolution; (f) finishing of the final three-dimensional printed object is not satisfactory; (g) digital mold generation is not disclosed; (h) comparison of the digital mold and digitally generated three-dimensional model is not disclosed; and (i) the purpose and utility for making holes is for mold removal.

A solution to this problem is achieved in the present invention by providing a method for generating a mold and having the thickness of the mold layer as thin as possible. Thin mold layer is subsequently easy to remove. Further, the digitally generated mold is compared with the three-dimensional model and then combined with the digital mold. The thickness of the mold layer is between about 0.1 mm to about 10 mm. The mold comprises the holes or perforations from which moisture or solvents can escape to facilitate drying of the object. A method of digitally generating a mold having a thin layer and holes is used for fabricating three-dimensional objects with high precision and quality.

The present application addresses the above mentioned concerns and short comings with regard to providing an improved a method of generating mold for fabricating high quality and precise three dimensional object.

SUMMARY OF THE INVENTION

This invention relates to three-dimensional printing and in particular to molds and methods for generating a mold and printing a three-dimensional object. The mold thickness is controlled and holes are generated in the mold surface for facilitating moisture or solvent release for drying of the printed object. The mold surface having holes is designed initially digitally and then combined with the three-dimensional model before printing the three-dimensional object on a layer by layer basis by sequentially printing a layer of the mold followed by a layer of a crafting medium contained within the contents of the mold layer. The process is then repeated until the object (mold plus crafting medium) is printed. The thickness of the mold is carefully controlled to maintain the overall quality of the three-dimensional object. When the model is enclosed inside the mold, there can be some residue moisture or solvent in the model even if steps are taken to minimize this with layer by layer drying concurrent with the printing. A solution of these challenges is provided by layer by layer printing of a mold and crafting medium with a thin skin thickness mold layer, generally between about 0.1 mm to about 10 mm thickness having holes or perforations of about 8. A mold according to claim 7 wherein said perforations have a diameter from about 0.1 mm to about 0.4 mm. The holes are evenly distributed on the mold. A method of digitally generated a mold having thin layer and holes is used for fabricating three dimensional objects with high precision and quality.

The present invention relates to a mold for a three-dimensional object printed from a crafting medium, said mold comprising:

(a) one or more mold layers, wherein each of the one or more mold layers substantially surrounds a corresponding crafting medium layer (b) of the object.

In further embodiments, present invention relates to a mold wherein the mold layers substantially conforms to the shape of the object.

In further embodiments, present invention relates to a mold wherein the mold layer comprises a thermoplastic polymer.

In further embodiments, present invention relates to a mold wherein the thermoplastic polymer is selected from the group consisting of poly(propylene), poly(styrene), poly(lactic acid) (PLA), acrylonitrilebutadiene-styrene (ABS), polycarbonate abs (PC-ABS), nylon, poly(carbonate), poly(phenyl sulfone), ultem, poly(ethylene), acrylic [poly(methyl methacrylate)], poly(benzimidazole), poly(ether sulfone), poly(etherether ketone), poly(etherimide), poly(phenylene oxide), poly(phenylene sulfide), poly(vinyl chloride), poly(vinyldiene fluoride), poly(acetal), poly(vinyl acetate), poly(vinyl butyrate), poly(vinyl alcohol), poly(4-hydroxystyrene), poly(vinyl formate), poly(vinyl stearate), poly(acrylamide), poly(caprolactone), chitosan and combinations thereof.

In further embodiments, present invention relates to a mold wherein said mold has a skin thickness from about 0.1 to about 10 mm.

In further embodiments, present invention relates to a mold wherein said mold has a skin thickness from about 0.2 to about 2 mm.

In further embodiments, present invention relates to a mold wherein said mold has a skin thickness from about 0.5 to about 1 mm.

In further embodiments, present invention relates to a mold wherein said mold comprises one or more perforations.

In further embodiments, present invention relates to a mold wherein said perforations have a diameter from about 0.1 mm to about 0.4 mm.

In further embodiments, present invention relates to a mold wherein the crafting medium comprises:

-   -   (i) from about 40% to about 80% by volume basis of a powder         selected from metal powders, ceramic powders, and combinations,         thereof;     -   (ii) from about 0.5% to about 10% by volume of a binder; and     -   (iii) from about 15% to about 60% by volume of an aqueous         solvent.

In further embodiments, present invention relates to a mold wherein the crafting medium comprises:

-   -   (i) from about 40% to about 80% by volume basis of a powder         selected from metal powders, ceramic powders, and combinations,         thereof;     -   (ii) from about 0.5% to about 10% by volume of a binder; and     -   (iii) from about 15% to about 60% by volume of a non-aqueous         solvent.

In further embodiments, present invention relates to a mold wherein the metal or ceramic powder of the crafting medium comprises particles having a size in the range from 0.1-100 micrometers.

In further embodiments, present invention relates to a mold wherein the metal powder of the crafting medium is selected from silver, gold, copper, tin, nickel, chromium, zinc, tungsten, cobalt, aluminum, molybdenum, boron, iron, titanium, vanadium, niobium, silicon, manganese, steel, metal alloys, and combinations thereof.

In further embodiments, present invention relates to a mold wherein the ceramic powder of the crafting medium is selected from silicon carbide, boron carbide, aluminum carbide, tungsten carbide, titanium carbide, tantalum carbide, silicon nitride, boron nitride, aluminum nitride, titanium nitride, zirconium nitride, steatite, forsterite, alumina, zircon beryllia, magnesia, mullite, cordierite, aluminum titanate, zirconia, and combinations thereof.

In further embodiments, present invention relates to a mold wherein the binder is selected from organic binders, inorganic binders, and combinations thereof.

In further embodiments, present invention relates to a mold wherein the in organic binder is selected from epoxy, polyurethane, agar-agar, starch, cellulosic materials, arrow root, Agar (E406), Alginic acid (E400), Sodium alginate (E401), Carrageenan (E407), Gum arabic (E414), Gum ghatti, Gum tragacanth (E413), Karaya gum (E416), Guar gum (E412), Locust bean gum (E410), Beta-glucan, Chicle gum, Dammar gum, Glucomannan (E425), Mastic gum, Psyllium seed husks, Spruce gum, Tara gum (E417), Gellan gum (E418), Xanthan gum (E415), polyethylene oxide, polycarboxylic acids (polyacrylic acid), polycarboxylates, polyvinyl alcohol, cellulose gum (Aquacel GSA and Aquacel GSH), hydroxymethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, and combinations thereof.

In further embodiments, present invention relates to a mold wherein the inorganic binder is selected magnesium oxide, magnesic, cement, sorel cement, inorganic salts, and combinations thereof.

In further embodiments the present invention relates to a crafting medium wherein said aqueous solvent is selected from water, or water in combination with one or more non-aqueous solvents selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, acetone, acetaldehyde, ethyl acetate, C2-C4 diols, glycerol, acetonitrile, C4-alcohols, 2-ethoxyethanol, 2-ethyl hexanol, 1,2-dichloroethane, diisopropyl amine, isoamyl alcohol, propyl acetate, isopropyl acetate, and mixtures thereof. Also, contemplated are azeotropes.

In further embodiments, the present invention relates to a crafting medium wherein said non-aqueous solvent is selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, acetone, acetaldehyde, ethyl acetate, C2-C4 diols, glycerol, acetonitrile, C4-alcohols, 2-ethoxyethanol, 2-ethyl hexanol, 1,2-dichloroethane, diisopropyl amine, isoamyl alcohol, propyl acetate, isopropyl acetate, and mixtures thereof.

In further embodiments, present invention relates to a mold wherein each of the one or more mold layers comprises a structural additive that substantially prevents undesired fusing of the crafting medium to a further crafting medium area during subsequent sintering.

In further embodiments, present invention relates to a mold wherein the structural additive is selected from the group consisting of metal particles, ceramic particles, charcoal particles and combinations thereof.

In further embodiments, present invention relates to a mold wherein the metal particles are selected from silver, gold, copper, tin, nickel, chromium, zinc, tungsten, cobalt, aluminum, molybdenum, boron, iron, titanium, vanadium, niobium, silicon, manganese, steel, metal alloys, and combinations thereof.

In further embodiments, present invention relates to a mold wherein the ceramic particles are selected from silicon carbide, boron carbide, aluminum carbide, tungsten carbide, titanium carbide, tantalum carbide, silicon nitride, boron nitride, aluminum nitride, titanium nitride, zirconium nitride, steatite, forsterite, alumina, zircon beryllia, magnesia, mullite, cordierite, aluminum titanate, zirconia, and combinations thereof.

In further embodiments, present invention relates to an object prepared using a mold of the present invention.

In further embodiments, present invention relates to such an object prior to sintering.

In further embodiments, present invention relates to a method for three-dimensionally printing a paste-based crafting model comprising the steps of:

-   -   (a) depositing a mold layer from a print head having a skin         thickness from about 0.1 mm to about 10 mm, and     -   (b) depositing a layer of a crafting medium with a print head         within the confines of the mold layer.

In further embodiments, present invention relates to a method further comprising the step of

-   -   (c) drying the deposited layer from step (b) with a drying         means.

In further embodiments, present invention relates to a method wherein steps (a), (b), and (c) are performed prior to deposition of a further crafting medium layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. 1 depicts a schematic representation of the system in accordance with the present invention.

FIG. 2 illustrates a digitally generated mold surface including holes in accordance with the present invention.

FIG. 3A illustrates a combination of the mold surface having holes and a crafting medium for a three-dimensional object, such as a prosthetic hip joint, after printing.

FIG. 3B illustrates a three-dimensional object, a prosthetic hip-joint, fabricated using a method of generating a mold in accordance with the present invention.

FIG. 4 illustrates a final finished prosthetic hip-joint prepared by the present invention.

FIG. 5 illustrates by a flow chart an example of a method for generating a mold and then printing a three-dimensional object in accordance with the present invention.

FIG. 6 illustrates a part that takes on the shape of the outer surface of the mold material FIG. 6A, and the resulting object before sintering, FIG. 6B.

FIG. 7 illustrates a schematic example of a sequence of layers comprising lines of extrusion.

FIG. 8A illustrates a mold in a box geometry containing a crafting material of an object.

FIG. 8B illustrates a thin shell mold with optional supports.

FIG. 9 illustrates multiple layers or lines of the mold material.

DETAILED DESCRIPTION OF THE INVENTION

In the view of the foregoing disadvantages inherent in the known types of methods and systems for three-dimensional printing now present in the prior art, the present invention provides an improved method and system for three-dimensional printing of heavy and complex structure using a support edifice. As such, the general purpose of the present invention, which will be described subsequently in greater detail, is to provide a new and improved method and system for three-dimensional printing of heavy and complex structure which has all the advantages of the prior art and none of the disadvantages.

In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that the embodiments may be combined, or that other embodiments may be utilized and that structural and logical changes may be made without departing from the spirit and scope of the present invention.

Three-dimensional printing has evolved from automation production, which started in the early 20th century. Automation production was applied in mechanical model preparation and the automotive industries. Recently, its applications were explored for other industries, including, medicine, fields related to medicine, construction, aerospace, etc. Three-dimensional printing is also promising for civil structures, including building and bridges. Many other industries and applications are also now developed for three-dimensional printing. Recently fabrication of artificial body parts by using three-dimensional printing are also on the rise. However, it is challenging to prepare complex three-dimensional objects. Many times the preparation requires preparing a thick mold wall or molding layer, or even a mold having a box-like structure, which can be difficult to remove during the post processing of the printed object. The mold should be removed in the first post processing step, and it is important that there is as little residue as possible left on the desired object after removing the mold. Furthermore, there is another challenging area, when the model is enclosed inside the mold; there can be some residue moisture or solvent in the model even if a drying apparatus can improve removal of the moisture or solvent by drying on a layer by layer basis. Residual moisture or solvent can affect the final quality of the part. A solution to this problem is provided in the present patent application. The present patent application is focused on providing a novel and improved method for generating a mold and the molds so generated. One of the solutions for the above mention problem of residual moisture or solvent is to control the mold thickness in high detail (precision). One can according to the present invention describe the thickness needed and the digital method for generating the mold for all layers of the mold. As another solution the present invention provides for perforations or small holes in the mold so that the moisture and residual solvent can escape. It is important that the mold with the holes/structure should allow for moisture travel without affecting the quality of the surface of the print. The mold material can be a thermoplastic or any polymeric or plastic material. Optionally, the mold material can also include the structural additives such as metal, charcoal particles, ceramic, or other particles. The structural additives can be useful in preventing the fusing of two crafting medium parts with each other upon sintering. The crafting medium is preferably a commercially available metal clay usually comprising very small particles of a metal such as silver, gold, bronze, or copper mixed with an organic binder and water commonly used in making jewelry, beads and small sculptures.

FIG. 1 depicts a schematic representation of the system for drying a paste based crafting model during three-dimensional printing according to one of the embodiments of the present invention. The system 100 of fabricating a three-dimensional object using a support edifice and also using a mold material with structural additives comprises: (a) supply arrangement for a filament material 101; (b) an extruder 103; (c) a feeding channel 106; (d) a plurality of nozzles 107 and 113; (e) a plurality of heating elements/systems 108 for melting the filament and 119 for drying the crafting medium; (f) a plurality of discharge orifices 109 and 114; (g) a supply arrangement for a crafting medium 110; (h) an actuator 112 for controlling the flow of the crafting medium; (i) a mold 116; and (j) a platform 115 on which the system of three-dimensional printer is fixed. The system has dual printhead which comprise a first dispensing nozzle 107 for depositing the filament 102 in flowable fluid form by the discharge orifice 109 to supply a filament 102 or a first material layer and a second dispensing nozzle 113 for depositing a crafting medium 111 or the second material layer which is in a paste form by the discharge orifice 114. The system further comprises a holding element 118 which holds a dual printhead and a heating element/system 119.

The system also comprises a filament feeding device comprising a stepper motor (not shown) and idler rollers 104 and 105 located opposite to drive rollers which work together to grip the filament there between and to advance it through a filament feeding channel 106 thereby regulating the flow of filament through the feeding channel. The extruder 103 can be of different types such as rollers, a gear system, etc. The heating system 121 can comprise a radiating heater, and further an air circulation fan. The heating system can also have connectors 120, which can be of electric wire or pipes/tubes for blowing air. The heating system can also provide cooling or a means to regulate or reduce the temperature and can function as a temperature control system. Further, the temperature control system can include without limitation one or more of a heater, coolant, a fan, a blower, or the like.

The feeding channel 106 is made of a material having low thermal conductivity, such as for example Teflon. The system can further include a first dispensing nozzle 107 preferably made of a material having a thermal conductivity greater than 25 W/(m·K), such as for example brass or similar metallic alloys. The first dispensing nozzle 107 can be heated to a temperature sufficiently high for the filament 102 to liquify. Heating elements 108, in the form of a resistance heating tape or sleeve, and a temperature sensor (not shown) can be arranged around a lower portion of the nozzle 107 to regulate the temperature of the nozzle 107 to a temperature of approximatively between 200° C. to 240° C. to convert a leading portion of the filament 102 into a flowable fluid state. The solid (un-melted) portion of the filament 102 inside the feeding channel 106 serves as a piston to drive the melted liquid for dispensing through a first discharge orifice 109. The drive motor (not shown) can be controlled to regulate the advancing rate of the filament 102 in the feeding channel 106 so that the volumetric dispensing rate of the fluid can be closely controlled.

As shown in the FIG. 1, the apparatus further includes a supply means 110 of crafting medium 111, such as for example a metal clay or a ceramic clay. In a preferred embodiment of the invention, the crafting medium 111 comprises microscopic metal particles of metals such as silver, gold, copper or alloys or combinations thereof, mixed with an organic binder and water. The supply means 110 is preferably shaped as a conventional clay extruder comprising a cylindrical cavity and valve means 112 to control and regulate the flow of crafting medium toward a second dispensing nozzle 113 and through a second discharge orifice 114.

Both nozzles 107 and 113 are arranged at a predetermined distance from an object supporting platform 115. The dual printhead and the platform 115 are moved relative to one another in a movement pattern corresponding to the parameters of the predetermined object 117. The fused filament is deposited through the first discharge orifice 109 while the dual printhead is moving in an X-Y-plane relative to the platform 115, to build one layer of a mold 116. Thereafter, the crafting medium 111 is deposited while the dual printhead is moving in an X-Y-plane relative to the platform 115 to fill the layer of the mold 116 that has just been deposited.

The crafting medium 111 is in paste form. The layer of the crafting medium is optimally dried immediately or as soon as possible after being deposited, and in an event before depositing of a further crafting medium layer. The system 100 can therefore include a heating system or drying apparatus 119, which can be connected on the printhead. The heating system is used for drying a paste of the crafting medium 111. By moving the heating system it is possible after finishing each layer of the object (both mold and paste), to repeatedly scan the printed layer and apply heat and air circulation to improve drying in a controlled way. The drying apparatus can comprise a radiating heater, and possibly an air circulation fan, which can facilitate better evenness in the drying and reduce risks for cracks and also reduce potential problems in the next steps.

Thereafter the dual printhead and the platform 115 are displaced in the Z-direction from one another by a distance corresponding to the thickness of a single layer so that the next layer can be deposited. The first and second dispensing nozzles 107 and 113 are used to deposit the fused filament and the crafting medium respectively and therefore alternate the deposition on a layer by layer basis, in such a manner that the mold is alternately built and then filled with crafting medium for each single layer. When the deposition is completed, the object 117 is embedded inside the mold 116. The mold 116 is subsequently removed to release the object 117. The removal step is preferably achieved by heating the mold 116 to a temperature of approximately 200° C. until the mold material is melts away from the object 117. If the object 117 is made of a metal clay paste, the metal contained in the object 117 is thereafter sintered to obtain a pure metal object. During the three-dimensional printing of these objects requiring support, a support edifice is also prepared simultaneously while printing the crafting material and mold on a layer by layer basis. The material used for the support edifice survives during the post processing. The mold material mixed with the structural additive is intended to survive the post processing steps and to prevent the individual parts such as the support edifice from fusing together with the desired objects. In alternative embodiments where the final object comprises two or more non-connected, but interspersed objects, e.g. such as freely moveable links of a chain, the structural additive mixed with the mold material prevents the fusing of the two or more parts of the object.

A first supply of filament material used to build the mold. The supply of filament can comprise a rotatable spool on which the filament is wound. Such a filament material can comprise, but is not limited to, one or more of the following materials including various waxes, thermoplastic polymers, thermoset polymers, and combinations thereof. However, the primary modeling material preferably comprises an organic polymer with structural additive. As described above, the filament material is preferably a thermoplastic polymer that softens and liquifies for easy deposition and which rapidly cools and hardens to provide a suitable mold. Thermoplastic polymers useful for forming the mold from the filament material can include the following: poly(propylene), poly(styrene), poly(lactic acid) (PLA), acrylonitrilebutadiene-styrene (ABS), polycarbonate abs (PC-ABS), nylon, poly(carbonate), poly(phenyl sulfone), ultem, poly(ethylene), acrylic [poly(methyl methacrylate)], poly(benzimidazole), poly(ether sulfone), poly(etherether ketone), poly(etherimide), poly(phenylene oxide), poly(phenylene sulfide), poly(vinyl chloride), poly(vinyldiene fluoride), poly(acetal), poly(vinyl acetate), poly(vinyl butyrate), poly(vinyl alcohol), poly(4-hydroxystyrene), poly(vinyl formate), poly(vinyl stearate), poly(acrylamide), poly(caprolactone), chitosan and combinations thereof. The structural additive is selected from the group consisting of metals, charcoal particles, ceramics, or other particles.

A second supply of crafting medium can be in paste form. Such a medium can comprise silicone, a ceramic material or the like. The crafting medium is preferably a commercially available metal clay usually consisting of very small particles of metal such as silver, gold, bronze, or copper mixed with an organic binder and water commonly used in making jewelry, beads and small sculptures.

FIG. 2 illustrates a mold surface including holes in accordance with the present invention. FIG. 2 depicts a mold surface design 200 which is generated digitally before starting the three-dimensional printing. The thickness, i.e. the skin thickness of the mold 201 can be 0.1 to 10 mm. Further, the holes 202 are made up of having 0.1 to 0.4 mm diameter. The holes 202 should be evenly distributed over the mold surface 201. The diameter of the holes is such small enough to prevent the high viscous paste to get through, but still allows moisture or solvent escape. Also, the holes are large enough to be crafted from the mold material. The three-dimensional object prepared from the mold surface design 200 is illustrated as an artificial hip-joint.

FIG. 3A illustrates a combination of the mold having holes and a crafting medium for a three-dimensional object. FIG. 3A depicts a three-dimensional object which is printed using the system as shown in FIG. 1. Further, the different elements or components of the system are explained in detailed above. The three-dimensional object 300, hip-joint, is printed by layer-by-layer depositing a mold material and a crafting material. The method of generating mold surface is explained in detail below (in FIG. 5). FIG. 3A depicts the three-dimensional object after the printing and before performing the post processing steps. The three-dimensional object 300 comprises a mold surface 301 including holes 302 and crafting material layers 303. FIG. 3A depicts the three-dimensional object, hip-joint. This object requires having some gap/space 304 between the cup 305 and ball 306 (where the ball meets the cup). The crafting medium is preferably a commercially available metal clay usually comprising very small particles of metal such as silver, gold, bronze, or copper mixed with an organic binder and water. The molding material can be selected from a suitable polymeric material as described herein. Further, in an alternate example, the molding material can also include structural additives such as metal, charcoal particles, ceramic, or other particles. The gap/space 304 between the cup 305 and ball 306 (where the ball meets the cup) can be achieved by using the mold material mixed with the structural additive, because the structural additive would prevent fusing of the cup 305 with the ball 306 upon sintering. The structural additives can be selected from materials such as metal, charcoal particles, ceramic, or other particles. After the post processing the mold surface 304 will have a residue of the structural additives. This residue will prohibit the cup 305 and the ball 306 of the hip joint from fusing during the post processing steps. Further, many other movable joints of different types such as hinges, pivots, gliding areas, saddles, and planar areas, and many other complex geometries can also be fabricated by using the structural additives. FIG. 3B illustrates a three-dimensional object 300, a hip-joint, fabricated using a method of generating mold in accordance with the present invention. FIG. 3B is a illustration of the hip-joint 300 including a cup 305, a ball 306, and a hip 307. FIG. 3B depicts the three-dimensional object 300, hip-joint, after performing all the post processing steps and it is in a completely finished state. The detail method of generating three-dimensional object according to the present invention is described below.

FIG. 4 illustrates a final finished hip-joint 400. This illustrates the view of the final finished three-dimensional product, hip-joint, prepared by using the three-dimensional printing method and how it can be incorporated into the human body

FIG. 5 illustrates by a flow chart an example of a method for generating a mold and then printing a three-dimensional object in accordance with the present invention. The method starts with providing a three-dimensional model to the computer or any digital media, at block 501. Then digitally generating the mold as per block 502. At block 503, combining the digitally generated mold and three-dimensional model. This step is one of the important steps of the present invention, it compares the three-dimensional parameters of the digitally generated mold and the three-dimensional model. Then the system generates the detailed tool paths and extrusion instructions at the block 504. The system also finalizes the thickness of the mold required and it selects the mold to be as thin as possible for providing a precise molding surface and easy removal, while also providing sufficient structural integrity for the object to be printed. The thickness of the mold surface, i.e. the skin can be 0.1 to 10 mm. Further, the perforation or holes are made up of having a diameter from about 0.1 mm to about 0.4 mm. The holes should be evenly distributed over the mold surface. Then the instructions are sent to the printer or a system (as explained above and depicted in FIG. 1). Then the apparatus/printer starts printing of the combined mold and three-dimensional model layer by layer, at described in block 506. At block 507, extrusion and deposition of a mold material (filament material) with an optional structural additive, and the crafting material layer is performed on a layer by layer basis. In the block 507, there are several sub-steps involved (which are not depicted in FIG. 5): such as providing a supply of mold building material in filament form; feeding the filament to enter one end of a flow passage of the first dispensing nozzle having a first discharge orifice on another end; heating the first dispensing nozzle to convert a leading portion of the filament therein to a flowable fluid; and dispensing the flowable fluid through the first discharge orifice to an object-supporting platform. Further, in block 507, there are several sub-steps involved: such as providing a supply of crafting medium in paste form; feeding the crafting medium to enter one end of a flow passage of the second dispensing nozzle having a second discharge orifice on another end; and during the dispensing step, operating the second dispensing nozzle for extruding the crafting medium on a layer.

At block 508, a drying apparatus or heating system 121 is performed. The heating system or drying apparatus can optionally be connected on the printhead. Then in the next step 509, heating system or drying apparatus is circulated on the crafting material layer to drying the crafting medium. By performing this drying on a layer by layer basis it is possible after finishing each layer of the object (both mold and paste), to improve drying in a controlled way. Furthermore, air circulation can be employed to facilitate drying. This drying will enable better evenness in the drying and reduce risks for cracks and also reduces problems in the next steps.

The holes generated on the mold surface can facilitate remaining moisture or solvent to escape even after the layer is finished. The holes are evenly distributed on the mold surface. The thickness of the mold surface, i.e. the mold skin can be about 0.1 mm to 10 mm and the diameter of the holes can be 0.1 to 0.4 mm diameter. The diameter of the holes is such to be small enough to prevent the high viscous paste to get through, but still large enough to permit moisture or solvent escape. Also, the holes are of a sufficient diameter large enough to allow them to be crafted from the mold material. In case, the mold surface thickness is too large then it will be difficult to remove during the post processing step. Further, if the mold is too thick, it can affect the quality of the three-dimensional object.

Then the “Turn off” command for the heating system or drying apparatus 121 is performed after drying as indicated at block 510. Next at block 511, thereafter the dual printhead and the platform are displaced in the Z-direction from one another by a distance corresponding to the thickness of a single layer so that the next layer can be deposited. Next at block 512, if the printing of the all layers, meaning that the crafted object and mold is complete then the process moves to the next step, block 513. Otherwise, the process repeats again from block 507 until the mold and crafting medium layers have been printed to complete the object.

At block 513, the processing step involves the removing of the mold material. The mold material can be removed by for example burning or melting or by chemical means, such as dissolution of the mold with a solvent. These removal means are easier if thinner layer. The next processing step is to remove the binder material from the crafting medium layers, as described by block 514. At block 515, the crafting material is transform to the final finish product.

Further, in an alternate example, the molding material may can include the structural additive such as metals, charcoal particles, ceramic, or other particles. The addition of the structural additives to the mold is such that it prevents the fusing of the object (crafting layer) with the support structure material or another crafting medium layer intended to be kept separate. For example, in a scenario, the material of the structural additive also prevents the fusing between one part of an object with another part of the object to create gap or space between them, as with the cup 305 and ball 306 of the prosthetic hip part 300.

The present invention relates to a three-dimensional imaging process for making objects, preferably metal objects or ceramic objects, on a layer-by-layer basis under the control of a data processing system. Some of the process steps which are not included above in detail are: (a) providing a dual printhead including a first dispensing nozzle and a second dispensing nozzle; (b) during the dispensing step, moving the dual printhead and the object-supporting platform relative to one another in a plane defined by first and second directions and in a third direction orthogonal to said plane to form the flowable fluid into a three-dimensional hollow pattern having a molding cavity shaped in accordance with a predetermined three dimensional object; (c) by layer basis through the second discharge orifice onto the three-dimensional hollow pattern in order to gradually fill the molding cavity, thereby forming the predetermined three-dimensional object; and (d) removing the three-dimensional hollow pattern in order to release the predetermined three-dimensional object.

Where the structural additive to the mold material is of the same or similar type as the main structural component of the crafting material, the processing step of removing the binder and the mold supporting material will result in a part that takes on the shape of the outer surface of the mold material, and then ultimately the resulting part will sinter as a whole.

In this embodiment the generation of the mold will have a negative inset thickness of 0.4-1.2 mm. The amount of additive in this case can be tailored to have same or less volume density in comparison to the volume density of the same/similar structural component of the crafting material. FIG. 6A illustrates a cross-section of a material with a crafting medium 303 in the center, surrounded by a mold material 301 that has the same additive as the crafting medium. The thickness of the mold is the mold inset thickness as represented by 301. FIG. 6B illustrates the resulting object before sintering 603.

FIG. 7 illustrates multiple layers forming a single outer shell mold 301 with greater depth to address the challenges presented by a negative mold shape and resulting voids. When crafting the object with the deposition of a mold material and a crafting medium 303, the part can be analyzed. In some instances several layers of the mold material can be deposited before a layer of the crafting material is deposited, where the thickness of the crafting material layer is the same as the sum of thickness of the previous multiple mold material layers deposited. Such a technique can reduce the time for crafting the object without loss in accuracy and definition of the resulting object. The optimization is dependent on the possibility to reliable fill any void resulting from a negative overhang angle. FIG. 7 illustrates a sequence of layers comprising lines of extrusion. The left hand-portion of the dotted line 701 shows that the angle is acceptable to have two layers of mold for each layer of crafting material. The right-hand portion of the dotted line 702 shows that the negative angle is too steep, such that there is a correspondence of one layer of mold to one layer of crafting material.

FIGS. 8A and 8B illustrate aspects for mold thickness and the use of a skin mold. Previously known methods for creating a mold and filling the mold in a layer by layer manner uses a solid mold with a simple geometrical outer surface such as a cube or cylinder. To speed up the process of removing the mold, and minimizing the risk for residue material, the mold of the present invention is a thin skin or shell. The shell is generated, preferably with a thickness of about 0.1 mm to about 10 mm. The thin shell can be supported by thin polymer supports where needed, which are subsequently removed in the post processing. FIG. 8A illustrates a simple mold 301 in a box geometry containing a hip implant prosthesis indicating the crafting medium 303 for the cup and ball aspects. FIG. 8B illustrates a thin mold shell or skin of the present invention, 301, with optional supports 801 where needed. The crafting medium 303 of the cup and ball aspects are shown. Note that any supports needed for post processing such as sintering are not included in the illustration.

It is important to control the thickness of the mold layer, because if the layer is too then, there is a risk of not having sufficient stiffness to support the crafting medium, whereas too thick of a layer will be difficult to remove in post processing. A deposition of a polymer by extrusion is feasible down to a width of about 0.1-0.2 mm. Generally, about 0.4 mm of mold thickness is needed for mold stability, which would require two lines of deposition if the extrusion is 0.2 mm wide. See FIG. 9 showing lines of the mold, 301, the crafting medium, 303, and an area with a two-line width of mold as indicated by 901.

The mold material is preferable using a polymer base, where the properties of this polymer base are such that it is easy to decompose or burn off or evaporate in the post processing steps, and yet has adhesion to the crafting material to support the combined structure until post process.

The adhesion between the mold material and the crafting material can further be improved by an additive in the mold material. The mold base material in PCL polymer has the advantage of good adhesion to a crafting material with a cellulose type or polysaccharide component. The mold base material in PLA polymer has the advantage of easily being decomposed or burned off or evaporated. A mix of several polymers and several additives can be selected to provide optimal performance.

Crafting Medium

Although a wide variety of crafting media can be used with the methods and systems of the present invention, a particularly useful crafting medium contains a very low concentration of the binder organic base materials, such as starches, cellulose, cellulose derivatives, agar, etc., and around 15 to 60 volume % water. The binding organic base material content can be varied from 1 to 10 volume %. The binder can act as glue between the powder particles, and also as filler between the particles. The method of preparation of the three-dimensional object also includes the step of drying on a layer-by-layer basis. The drying is a continuous process in the present invention and can remove most of the water and/or other solvents or carriers from the binder composite material from each layer after depositing.

An exemplary crafting material useful herein comprises:

(i) from about 40% to about 80% by volume basis of a powder selected from metal powders, ceramic powders, and combinations, thereof; (ii) from about 0.5% to about 10% by volume of a binder; and (iii) from about 15% to about 60% by volume of an aqueous solvent.

An exemplary crafting material useful herein comprises:

(i) from about 40% to about 80% by volume basis of a powder selected from metal powders, ceramic powders, and combinations, thereof; (ii) from about 0.5% to about 10% by volume of a binder; and (iii) from about 15% to about 60% by volume of a non-aqueous solvent.

Another crafting material useful herein comprises,

(i) from about 60% to about 70% by volume basis of a powder; (ii) from about 1% to about 5% by volume of a binder; and (iii) from about 25% to about 35% by volume of an aqueous solvent.

Another crafting material useful herein comprises,

(i) from about 60% to about 70% by volume basis of a powder; (ii) from about 1% to about 5% by volume of a binder; and (iii) from about 25% to about 35% by volume of a non-aqueous solvent.

The solvent or carrier for the crafting material can be an aqueous solvent. Such an aqueous solvent can be solely or primarily water, or can comprise other solvent materials which are generally water miscible. In other embodiments, a nonaqueous solvent or mixtures of non-aqueous solvents can be employed. Such non-aqueous solvents can be selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, acetone, acetaldehyde, ethyl acetate, C2-C4 diols, glycerol, acetonitrile, C4-alcohols, 2-ethoxyethanol, 2-ethyl hexanol, 1,2-dichloroethane, diisopropyl amine, isoamyl alcohol, propyl acetate, isopropyl acetate, and mixtures thereof. Also, contemplated are azeotropes.

Several materials can be used as the leaving component, i.e. the solvent or carrier, in the deposition technique involving continuous, layer-by-layer drying. One example of a departing component is water, with a vapor pressure of about 2.4 kPa. Higher vapor pressures may in general be preferred, as they will require less energy to drive them away from the deposited part. However, including materials with vapor pressures which are very high as compared to water (acetaldehyde, for example) may cause difficulties with layer-to-layer and strand-to-strand bonding if the leaving component departs prior to the formation of a significant bond. In this case controlled drying, can be achieved via depression of the print temperature and can be employed during forming of the part. After forming of the part, the temperature (or other thermodynamic variables) may be changed to complete the removal of the leaving component.

Solvents used can be aqueous (e.g., water, and water with salts or surfactants), organic and primarily carbon based, organic with halogen groups, organic with large amounts of fluorine, or mixtures of any of those aforementioned items. Mixtures of components can be chosen such that when the components leave the part, the components leave in a proportion identical or substantially similar to the proportion of the components in the deposited material.

In addition to the list provided below, materials such as dichloroethane, diiodoethane, fluorinated or chlorinated refrigerants, or degreaser materials as manufactured by DuPont (Operteron) or MicroCare (Tergo) may be used. Further, solvent drying specialty fluids added to liquids such as water or ethanol (and their mixtures), such as Vertrel XP10 Solvent Drying Specialty fluid by MicroCare, can be used.

In the three-dimensional printing process it is generally necessary to use the crafting medium in conjunction with binders to provide rigidity to the object during fabrication. Different types of binding materials are used in three-dimensional printing processes. Organic binders, such as epoxy, polyurethane, agar-agar, starch, cellulosic materials, Agar (E406), Alginic acid (E400), Sodium alginate (E401), Carrageenan (E407), Gum arabic (E414), Gum ghatti, Gum tragacanth (E413), Karaya gum (E416), Guar gum (E412), Locust bean gum (E410), Beta-glucan, Chicle gum, Dam mar gum, Glucomannan (E425), Mastic gum, Psyllium seed husks, Spruce gum, Tara gum (E417), Gellan gum (E418), Xanthan gum (E415), polyethylene oxide, polycarboxylic acids (polyacrylic acid), polycarboxylates, polyvinyl alcohol, cellulose gum (Aquacel GSA and Aquacel GSH), hydroxymethyl cellulose, hydroxypropyl cellulose, Carboxymethyl cellulose, etc. can be used while inorganic binders, such as magnesium oxides, magnesic, cement, sorel cement, salts, etc. are used. With the three-dimensional objects with a powder plus binder constitution for sintering there can be several problems. The binder can be difficult to remove because it needs to be dissolved or burned out after the object is finished. The binder can also be hazardous and could require toxic substances to dissolve it. While removing the binder there is a risk for cracks and deformities in the resulting object. Further, methods of three-dimensional printing using clay or ceramic materials and preparing molding are also well known in the prior art documents. Most of these prior art documents discuss the drying or heating of the mold or clay paste post processing. Problems such as cracking and unevenness can arise when the drying is carried out at the end of the processing. The present invention is also providing solution to solve the cracks and unevenness of the object.

A solution to this problem is achieved in the present patent application by providing a crafting medium comprising a metal or ceramic, binder organic base materials, and water. The crafting medium which is in the paste form includes 40 volume %-80 volume % metal/ceramic powder, 1 volume %-10 volume % organic base material, and 15 volume %-60 volume % water. The metal or ceramic powder particle size is in the range from 0.1-100 micrometers.

In another embodiment of the invention, the crafting medium comprises microscopic particles of metal, such as silver, gold, copper, tin, nickel, chromium, zinc, tungsten, cobalt, aluminum, molybdenum, boron, iron, titanium, vanadium, niobium, silicon, manganese, steel or alloys or combinations thereof, and also oxides from these metals, mixed with the binder organic base material and water. Also additional corrosion inhibitors, sintering aids or lubrication additives in the range of 0.1-2 volume % can be added.

In another embodiment, the powder is instead a ceramic powder such as silicon carbide, boron carbide, aluminum carbide, tungsten carbide, titanium carbide, tantalum carbide, silicon nitride, boron nitride, aluminum nitride, titanium nitride, zirconium nitride, steatite, forsterite, alumina, zircon beryllia, magnesia, mullite, cordierite, aluminum titanate and zirconia mixed with the binder organic base material and water. Also additional corrosion inhibitors, sintering aidis or lubrication additives in the range of 0.1-2 volume % can be added.

In such embodiments, the binder organic base material can be polyurethane, agar-agar, starch, cellulosic materials, Agar (E406), Alginic acid (E400), Sodium alginate (E401), Carrageenan (E407), Gum arabic (E414), Gum ghatti, Gum tragacanth (E413), Karaya gum (E416), Guar gum (E412), Locust bean gum (E410), Beta-glucan, Chicle gum, Dam mar gum, Glucomannan (E425), Mastic gum, Psyllium seed husks, Spruce gum, Tara gum (E417), Gellan gum (E418), Xanthan gum (E415), polyethylene oxide, polycarboxylic acids (polyacrylic acid), polycarboxylates, polyvinyl alcohol, cellulose gum (Aquacel GSA and Aquacel GSH), hydroxymethyl cellulose, hydroxypropyl cellulose, Carboxymethyl cellulose, or combinations thereof.

Sintering aids such as salts, gum rosin or pine rosin, isopropyl alcohol, Propylene glycol, Copper oxides, other metal oxides, low melting point metals or alkaline earth metals can be used. Lubricant aids such as essential oils, glycerin, zinc stearate or other stearates, carbon black, silica and ferrous oxide can be used. Corrosion inhibitors such as from the group consisting of the nitrate of lithium, sodium, potassium, calcium, magnesium, zinc, cobalt, iron, chromium, and copper, and the nitrite of lithium, sodium, potassium, calcium, magnesium, zinc can be used.

With the compositions and processes of the present invention, substantially all of the moisture, i.e. the water, and other solvent or carrier components for the binder of the crafting medium is removed immediately after deposition of each layer by use of the drying apparatus. By “substantially all of the moisture” is meant that at least about 90% by weight, and in further embodiments at least about 95% by weight, and yet in further embodiments at least about 99% by weight of the water and other solvent or carrier components are removed. This novel method of three-dimensional object building does not require the use of a post-processing debinding step. Further, the present invention also provides a system for drying a paste based crafting model during three-dimensional printing and method thereof. The drying apparatus or the heating system is connected to the moving print head. This makes drying possible after finishing each layer of the object (both mold and paste), the print head can repeatedly scan the printed layer and apply heat and air circulation to improve drying in a controlled manner.

EXAMPLES

The following examples further described and demonstrate embodiments within the scope of the present invention. The Examples are given solely for purpose of illustration and are not to be construed as limitations of the present invention, as many variations thereof are possible without departing from the spirit and scope of the invention.

Example 1: Crafting Medium and Process for Making

A crafting medium comprising the following components was prepared. The components are each on a volume % basis.

Stainless steel powder 17-4: 62%

Distilled water: 32%

Arrow root powder: 4%

Xanthan gum 1%

Polycarboxylate 1%

A premix of the water and arrow root is prepared by heated to 80° C. with stirring. The premix is then cooled to room temperature. A separate premix of xanthan gum and the polycarboxylate is made by combining them with stirring to form a thick paste. Next, the stainless steel powder and the xanthan gum premix are added to the arrow root premix and combined using a mechanical stirrer.

The resulting paste is useful for three-dimensional printing. The paste can be printed on a line-by-line and layer-by-layer basis in conjunction with a mold layer. Each deposited paste layer is dried according to the present invention. The resulting three-dimensional object is then subsequently debound and then sintered to provide the stainless steel three-dimensional object.

It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-discussed embodiments may be used in combination with each other. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description.

The benefits and advantages which may be provided by the present invention have been described above with regard to specific embodiments. These benefits and advantages, and any elements or limitations that may cause them to occur or to become more pronounced are not to be construed as critical, required, or essential features of any or all of the embodiments.

While the present invention has been described with reference to particular embodiments, it should be understood that the embodiments are illustrative and that the scope of the invention is not limited to these embodiments. Many variations, modifications, additions and improvements to the embodiments described above are possible. It is contemplated that these variations, modifications, additions and improvements fall within the scope of the invention.

INCORPORATION BY REFERENCE

The entire disclosure of each of the patent documents, including certificates of correction, patent application documents, scientific articles, governmental reports, websites, and other references referred to herein is incorporated by reference herein in its entirety for all purposes. In case of a conflict in terminology, the present specification controls.

EQUIVALENTS

The invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are to be considered in all respects illustrative rather than limiting on the invention described herein. In the various embodiments of the methods and systems of the present invention, where the term comprises is used with respect to the recited steps of the methods or components of the compositions, it is also contemplated that the methods and compositions consist essentially of, or consist of, the recited steps or components. Furthermore, it should be understood that the order of steps or order for performing certain actions is immaterial so long as the invention remains operable. Moreover, two or more steps or actions can be conducted simultaneously.

In the specification, the singular forms also include the plural forms, unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In the case of conflict, the present specification will control.

Furthermore, it should be recognized that in certain instances a composition can be described as being composed of the components prior to mixing, or prior to a further processing step such as drying, binder removal, heating, sintering, etc. It is recognized that certain components can further react or be transformed into new materials.

All percentages and ratios used herein are on a volume (volume/volume) or weight (weight/weight) basis as shown, or otherwise indicated. 

1. A mold for a three-dimensional object printed from a crafting medium, said mold comprising: (a) one or more mold layers, wherein each of the one or more mold layers substantially surrounds a corresponding crafting medium layer (b) of the object.
 2. The mold according to claim 1 wherein the one or more mold layers substantially conform to the shape of the object.
 3. The mold according to claim 1 wherein the mold layer comprises a thermoplastic polymer.
 4. The mold according to claim 3 wherein the thermoplastic polymer is selected from the group consisting of poly(propylene), poly(styrene), poly(lactic acid) (PLA), acrylonitrilebutadiene-styrene (ABS), polycarbonate abs (PC-ABS), nylon, poly(carbonate), poly(phenyl sulfone), ultem, poly(ethylene), acrylic [poly(methyl methacrylate)], poly(benzimidazole), poly(ether sulfone), poly(etherether ketone), poly(etherimide), poly(phenylene oxide), poly(phenylene sulfide), poly(vinyl chloride), poly(vinyldiene fluoride), poly(acetal), poly(vinyl acetate), poly(vinyl butyrate), poly(vinyl alcohol), poly(4-hydroxystyrene), poly(vinyl formate), poly(vinyl stearate), poly(acrylamide), poly(caprolactone), chitosan and combinations thereof.
 5. The mold according to claim 1, wherein said mold has a skin thickness from about 0.1 to about 10 mm.
 6. The mold according to claim 1, wherein said mold has a skin thickness from about 0.2 to about 2 mm.
 7. The mold according to claim 1, wherein said mold has a skin thickness from about 0.5 to about 1 mm.
 8. The mold according to claim 1, wherein said mold comprises one or more perforations.
 9. The mold according to claim 8 wherein said one or more perforations have a diameter from about 0.1 mm to about 0.4 mm.
 10. The mold according to claim 1 wherein the crafting medium comprises: (i) from about 40% to about 80% by volume basis of a powder selected from the group consisting of metal powders, ceramic powders, and combinations, thereof; (ii) from about 0.5% to about 10% by volume of a binder; and (iii) from about 15% to about 60% by volume of an aqueous solvent.
 11. The mold according to claim 1 wherein the crafting medium comprises: (i) from about 40% to about 80% by volume basis of a powder selected from the group consisting of metal powders, ceramic powders, and combinations, thereof; (ii) from about 0.5% to about 10% by volume of a binder; and (iii) from about 15% to about 60% by volume of a non-aqueous solvent.
 12. The mold according to claim 10 wherein the metal or ceramic powder of the crafting medium comprises particles having a size in the range from 0.1-100 micrometers.
 13. The mold according to claim 10 wherein the metal powder of the crafting medium is selected from the group consisting of silver, gold, copper, tin, nickel, chromium, zinc, tungsten, cobalt, aluminum, molybdenum, boron, iron, titanium, vanadium, niobium, silicon, manganese, steel, metal alloys, and combinations thereof.
 14. The mold according to claim 10 wherein the ceramic powder of the crafting medium is selected from the group consisting of silicon carbide, boron carbide, aluminum carbide, tungsten carbide, titanium carbide, tantalum carbide, silicon nitride, boron nitride, aluminum nitride, titanium nitride, zirconium nitride, steatite, forsterite, alumina, zircon beryllia, magnesia, mullite, cordierite, aluminum titanate, zirconia, and combinations thereof.
 15. The mold according to claim 10 wherein the binder is selected from the group consisting of organic binders, inorganic binders, and combinations thereof.
 16. The mold according to claim 15 wherein the in organic binder is selected from the group consisting of epoxy, polyurethane, agar-agar, starch, cellulosic materials, arrow root, Agar (E406), Alginic acid (E400), Sodium alginate (E401), Carrageenan (E407), Gum arabic (E414), Gum ghatti, Gum tragacanth (E413), Karaya gum (E416), Guar gum (E412), Locust bean gum (E410), Beta-glucan, Chicle gum, Dammar gum, Glucomannan (E425), Mastic gum, Psyllium seed husks, Spruce gum, Tara gum (E417), Gellan gum (E418), Xanthan gum (E415), polyethylene oxide, polycarboxylic acids (polyacrylic acid), polycarboxylates, polyvinyl alcohol, cellulose gum (Aquacel GSA and Aquacel GSH), hydroxymethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, and combinations thereof.
 17. The mold according to claim 15 wherein the inorganic binder is selected magnesium oxide, magnesic, cement, sorel cement, inorganic salts, and combinations thereof.
 18. The mold according to claim 10 wherein said aqueous solvent is selected from the group consisting of water, or water in combination with one or more non-aqueous solvents selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, acetone, acetaldehyde, ethyl acetate, C2-C4 diols, glycerol, acetonitrile, and mixtures thereof.
 19. The mold according to claim 11 wherein said non-aqueous solvent is selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, acetone, acetaldehyde, ethyl acetate, C2-C4 diols, glycerol, acetonitrile, and mixtures thereof.
 20. The mold according to claim 1 wherein each of the one or more mold layers comprises a structural additive that substantially prevents undesired fusing of an area of the crafting medium to a further area of the crafting medium during subsequent sintering of the object.
 21. The mold according to claim 20 wherein the structural additive is selected from the group consisting of metal particles, ceramic particles, charcoal particles and combinations thereof.
 22. The mold according to claim 21 wherein the metal particles are selected from the group consisting of silver, gold, copper, tin, nickel, chromium, zinc, tungsten, cobalt, aluminum, molybdenum, boron, iron, titanium, vanadium, niobium, silicon, manganese, steel, metal alloys, and combinations thereof.
 23. The mold according to claim 21 wherein the ceramic particles are selected from the group consisting of silicon carbide, boron carbide, aluminum carbide, tungsten carbide, titanium carbide, tantalum carbide, silicon nitride, boron nitride, aluminum nitride, titanium nitride, zirconium nitride, steatite, forsterite, alumina, zircon beryllia, magnesia, mullite, cordierite, aluminum titanate, zirconia, and combinations thereof.
 24. An object prepared using the mold of claim
 1. 25. The object according to claim 24 prior to sintering.
 26. A method for three-dimensionally printing a paste-based crafting model comprising the steps of: (a) depositing a mold layer from a print head, said mold layer having a skin thickness from about 0.1 mm to about 10 mm, and (b) depositing a layer of a crafting medium from a print head within the confines of the mold layer.
 27. The method for according to claim 24 further comprising the step of (c) drying the deposited layer from step (b) with a drying means.
 28. The method according to claim 27 wherein steps (a), (b), and (c) are performed prior to deposition of a further crafting medium layer. 